Ring lasers are used to measure angular velocity, displacement, or acceleration about particular axes. Frequently they measure such angular velocity about only one axis. However, three ring lasers may be made within a single laser block, and their output signals are useful in measuring angular velocity about three mutually perpendicular axes.
It is important that ring laser blocks used in ring laser gyros neither translate nor rotate with changes in temperature, for an error can be introduced, and it would not be apparent that the measured angular velocity, or other measurement, does not contain a component of such error signal. Further, when such blocks are supported by supports fabricated of material having a different temperature coefficient of expansion than the block itself, the block may be stressed by forces transmitted to the block at the points of connection between the support and the block.
The block is typically made of dimensionally stable inorganic pore-free glass ceramic material having both a glass-like and crystalline structure that results in a near-zero coefficient of thermal expansion. The support, however, is usually fabricated of a different material, typically a metal, having a different coefficient of thermal expansion. Because of the difference between the coefficients of expansion of the block and the support, there is a tendency for the support to transmit temperature-caused forces or torques to the block. Such forces or torques can internally stress the block, causing misalignment of optical components or of the block. Such misalignments frequently cannot be tolerated.